Plantas tóxicas que afetam o sistema nervoso: intoxicação por Ipomoea asarifolia em caprinos e ovinos; intoxicação por Hipochaeris radicata em cavalos.

Abstract

Ipomoea asarifolia causes a tremogenic syndrome in sheep, goats, cattle and buffaloes. The objectives of this experiment were to determine the toxicity to goats of fresh I. asarifolia collected during the raining and dry season, to determine the toxicity of the dry plant, to determine the toxicity of the plant to sheep, and to determine if the active principle is eliminated through milk. In the first experiment the plant collected in the dry and raining season was fed to 16 goats. The plant collected during the dry season causes clinical signs at the daily doses of 5 and 10g per kg body weight (g/kg bw). The plant collected during the raining season was toxic at the daily doses of 20 and 30g/kg bw, demonstrating that the plant is more toxic during the dry period. The dry plant collected in the dry season was fed to 9 goats at doses of 1.7, 2, 3.4 and 5.1 g/kg bw. Daily doses of 3, 4 and 5.1g/kg bw cause clinical signs, demonstrating that the plant maintains its toxicity after being dry. The fresh plant collected during the dry and raining season was fed to 10 sheep. The plant collected in the dry season was toxic at the dose of 5g/kg bw, and the plant collected in the raining season was toxic at the doses of 10 and 20 g/kg bw. These results suggest that sheep are more susceptible that goats to the intoxication. Because some farmers mentioned that young lactating, non grazing, lambs are poisoned by milk ingestion, I. asarifolia was fed at daily doses of 2.5, 5 and 10g/kg bw for variable periods to 5 sheep from the day of parturition (2 sheep), after the last day of pregnancy (1 sheep) and 60 days before parturition (2 sheep). The sheep but not the lambs showed clinical signs of intoxication suggesting that the active principle is not eliminated through the milk at toxic doses for the lambs. In one sheep euthanized there were no gross or histologic lesions. The main ultrastructural findings were found in Purkinje cell dendrites and included swelling, decrease or absence of dendritic spines, decrease or absence of neurotubules and neurofilaments and vacuolation of the dendroplasm. Swelling of the smooth endoplasmic reticulum and granular eletrondense inclusions in dendroplasm were observed. Swelling of the astrocyte foot processes was conspicuous. It is proposed that Ipomoea asarifolia have a toxin that induces excitotoxicity with neurological disturbances and morphological changes in Purkinje cell dendrites.